PRoACC
Post-Doctoral Research Programme on Adaptation to Climate Change

Summary Results PRoACC-1

The impacts of climate change in the Mekong basin are manifold: they work at multiple levels of time and space at all socio-economic and environmental sectors. In the four themes of PRoACC various adaptation issues have been studied. Below some of the main policy-relevant findings are highlighted per theme.

Basin hydrology and climate change adaptation

Postdoc mr. Jun Li (CAS, China) and post-graduate mr. Bikesh Shrestha (AIT, Bangkok)

The annual precipitation in the Lancang/Upper Mekong (China) surprisingly shows no significant trend although models expect an increase in the future. The variability, however, has increased: longer dry spells and increased heavy rainfall events with increased frequencies of droughts and floods as a result. This trend has grown stronger in the last few decades. Runoff has increased mainly due to changes in evapotranspiration, caused by less wind and higher humidity, likely land use changes. The uncertainty in predictions is still high. Improved monitoring and regional modeling will be needed to support adaptation in the region and downstream. Reservoir planning and operation have to be conducted with a view to limit the potential impacts of increased variability.

In the sub-basin Nam Ou in Laos the impact of climate change on sediment discharge has been studied, and the results probably apply to many other sub-basins of the Mekong. Due to different rainfall and (though not studied in detail) land use, the river will contain a higher sediment load with the changing climate. However, because of the planned reservoirs in the basin, the load will decrease substantially. Depending on the number of reservoirs and their management this might lead to a reduction of 80-95%. This far more than a compensation by the expected increase. It will be necessary to study the potential impacts of the reservoirs at basin level. The impacts of sediment trapping will extend from behind the dams (filling up of reservoirs) to after the dams, e.g. increased river erosion; reduced nutrients to critical ecosystems (e.g. Tonle Sap), and into the coastal areas (less sediment: coastal erosion and negative impacts on mangrove forests). Integrated sediment management along the Mekong will be needed to adapt to the changing climate and plan for the least negative impacts on impacts along the Mekong.

Urban areas and climate change adaptation

Postdocs mrs. Long (SIWRR, Vietnam) and mrs. Huong (INHEM, Vietnam)

Urbanisation influences local climate: Temperature is higher (urban heat island effect) and the intensity of heavy storms increases. Urban flooding in the Mekong delta has multiple causes: extreme rainfall, river floods, floods from the sea (strengthened by sea level rise, more severe surges). Multiple causes ask for differentiated measures. In some areas urban drainage needs improvement, including reservoirs and/or pumping stations. In other areas flood protection (dikes, embankments) might be extended. Local rainfall storage (rooftop, gardens, underground) can contribute to diminishing flood depth due to heavy rainfall (see e.g. Figure 2). But also non-structural measures are important: city planning, early warning and flood-proofing strategies can prevent unsustainable situations; awareness raising, flood drills, creating refuges etc. can limit the impacts. The Mekong Delta has an increasing demand for water in agriculture and shows changing rainfall patterns. Traditional sources (rain, groundwater and surface water) are insufficient in the near future. The study in Can Tho city shows that urban wastewater is sufficient to cover about 16% of water demand in rice cultivation. Co-benefits are the nutrients, which can cover 12% (Phosphorus) to 20% (Nitrogen) of the agricultural demand. Re-use at the same time limits pollution and treatment costs of wastewater. The study in Can Tho can be an example for other cities in low land situations.

The delta system in the light of climate change adaptation

Postdocs mrs. Cuc (WRU, Vietnam) and mr. Tri Van (Cantho University)

Climate change is leading to more extremes in runoff. Timely forecast and early warning are important adaptation options, next to structural and spatial planning measures. It is expected that the division of water over the Bassac and the Mekong in the Vietnam Mekong delta will change. Less water in the Bassac means less water for agriculture and aquaculture in the Ca Mau peninsula. The coastal area at the East Sea side will be heavily impacted by sea level rise (coastal erosion, flooding, salt water intrusion). In mangrove forests are a natural and effective protection against storms and wave attack. Wave attenuation depends on the width and health of the forest. A width of 1.5 km gives optimal decrease of wave height (see figure 3). The impacts of climate change on mangroves are uncertain, but decrease of sediment input, sea level rise and changes in river runoff all form severe threats. Local communities can play an important role in the management of the mangrove forests, but external support with knowledge, finances and regulations is necessary. These conclusions seem to be valid for all mangrove areas along the Vietnamese coast.

Analysis of adaptation institutions in rural China, Vietnam and Thailand

Postdocs mr. Hao Li (CWRC, China) and mr. Ram Bastakoti (AIT, Bangkok)

Existing policies related to climate change adaptation have been studied in China, Thailand and Vietnam. Local farmers have been interviewed to find out how they are stimulated or counteracted in adapting to climatic conditions by local, provincial and national regulations. A mixed picture emerges where sometimes government supports local adaptation initiatives; but existing regulations sometimes hinder local stakeholders in their attempts to adapt. In all cases stakeholders need support with knowledge (new and traditional) and finances (access to credit facilities) to be able to overcome prolonged periods of drought and to move towards more sustainable farming. This might require changed local, provincial and national institutional arrangements including adapted regulations. Although differences appear between the three areas in the two studies, the main conclusions seem to be generally applicable.

PRoACC key messages

  • Climate change impacts occur in the entire Mekong River Basin; they interact with other influences from global/regional changes and cannot easily be isolated.
  • With many reservoirs planned, integrated water-sediment management is necessary for the basin as a whole.
  • Droughts will occur more frequently both in upstream and downstream areas. Adaptation measures in agriculture are necessary. In urban areas, wastewater reuse for irrigation provides co-benefits (reuse of nutrients and water).
  • Flood risks are increasing (rivers and sea); caused by human interference in the basin, climate change and sea level rise; but also due to increasing developments in flood prone areas (people and assets). The Mekong Delta is a hot spot for flood adaptation. Soft measures, such as early warning, are important.
  • Mangrove forests are efficient in wave attenuation and coastal protection. They are threatened by many influences including climate change. Community based management is effective but needs government support. But, government support sometimes counteracts local adaptation initiatives.
  • Climate change adaptation requires action at multiple scales (basin, national, local). Riparian countries of the Mekong River basin can learn from each other's approaches. Enhanced and shared information supports cooperation in the area of climate change adaptation and related areas.